[Rdo-list] live block migration on el7

[Kashyap Chamarthy]

[Added Eric Blake and Michal Privoznik of libvirt project, in case if
they have more to add or correct me.]

On Fri, Nov 14, 2014 at 11:40:18AM -0600, David Martin wrote:
> We are running Havana on EL6, we rely pretty heavily on live storage
> migrations setup like so:
> block_migration_flag=VIR_MIGRATE_UNDEFINE_SOURCE,VIR_MIGRATE_PEER2PEER,VIR_MIGRATE_NON_SHARED_INC,VIR_MIGRATE_LIVE
> and it works great.
> 
> I am currently building a new stack based on EL7 and Juno,  however when I
> attempt to do a migration (nova live-migration --block-migrate x), i
> receive the following:
> libvirtError: internal error: unable to execute QEMU command 'migrate':
> this feature or command is not currently supported
> 
> I've found a couple of related BZs:
> https://bugzilla.redhat.com/show_bug.cgi?id=1022393
> https://bugzilla.redhat.com/show_bug.cgi?id=1020495
> 
> Am I understanding this correctly that they have completely removed this
> feature from RHEL7? Unless I'm running the RHEV variant of qemu-kvm??

AIUI, seems like your assessment is correct.

Reading the bugs, the summary is, in *EL6 the below QMP (QEMU Machine
Protocol) arguments to 'migrate' command

  "blk": block migration, full disk copy 
  "inc": incremental disk copy

were inadvertantly introduced. However, all the live block operations
should work with: qemu-kvm-rhev (the variant you allude to, above).

If you'd like to rebuild them for *EL variant distributions, the SRPMs
should be available at http://ftp.redhat.com.

-- 
/kashyap